On 3/5/19 10:34 AM, speck for Thomas Gleixner wrote:
> On Mon, 4 Mar 2019, speck for Jon Masters wrote:
> 
>> On 3/1/19 4:47 PM, speck for Thomas Gleixner wrote:
>>>       if (static_branch_unlikely(&vmx_l1d_should_flush))
>>>               vmx_l1d_flush(vcpu);
>>> +     else if (static_branch_unlikely(&mds_user_clear))
>>> +             mds_clear_cpu_buffers();
>>
>> Does this cover the case where we have older ucode installed that does
>> L1D flush but NOT the MD_CLEAR? I'm about to go check to see if there's
>> logic handling this but wanted to call it out.
> 
> If no updated microcode is available then it's pretty irrelevant which code
> path you take. None of them will mitigate MDS.

You're right. My fear was we'd have some microcode that mitigated L1D
without implied MD clear but also did MDS. I was incorrect - all ucode
that will be publicly released will have both properties.

Jon.

-- 
Computer Architect | Sent with my Fedora powered laptop